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1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Landlock - Credential hooks
4 *
5 * Copyright © 2019-2020 Mickaël Salaün <mic@digikod.net>
6 * Copyright © 2019-2020 ANSSI
7 * Copyright © 2021-2025 Microsoft Corporation
8 */
9
10#ifndef _SECURITY_LANDLOCK_CRED_H
11#define _SECURITY_LANDLOCK_CRED_H
12
13#include <linux/container_of.h>
14#include <linux/cred.h>
15#include <linux/init.h>
16#include <linux/rcupdate.h>
17
18#include "access.h"
19#include "limits.h"
20#include "ruleset.h"
21#include "setup.h"
22
23/**
24 * struct landlock_cred_security - Credential security blob
25 *
26 * This structure is packed to minimize the size of struct
27 * landlock_file_security. However, it is always aligned in the LSM cred blob,
28 * see lsm_set_blob_size().
29 */
30struct landlock_cred_security {
31 /**
32 * @domain: Immutable ruleset enforced on a task.
33 */
34 struct landlock_ruleset *domain;
35
36#ifdef CONFIG_AUDIT
37 /**
38 * @domain_exec: Bitmask identifying the domain layers that were enforced by
39 * the current task's executed file (i.e. no new execve(2) since
40 * landlock_restrict_self(2)).
41 */
42 u16 domain_exec;
43 /**
44 * @log_subdomains_off: Set if the domain descendants's log_status should be
45 * set to %LANDLOCK_LOG_DISABLED. This is not a landlock_hierarchy
46 * configuration because it applies to future descendant domains and it does
47 * not require a current domain.
48 */
49 u8 log_subdomains_off : 1;
50#endif /* CONFIG_AUDIT */
51} __packed;
52
53#ifdef CONFIG_AUDIT
54
55/* Makes sure all layer executions can be stored. */
56static_assert(BITS_PER_TYPE(typeof_member(struct landlock_cred_security,
57 domain_exec)) >=
58 LANDLOCK_MAX_NUM_LAYERS);
59
60#endif /* CONFIG_AUDIT */
61
62static inline struct landlock_cred_security *
63landlock_cred(const struct cred *cred)
64{
65 return cred->security + landlock_blob_sizes.lbs_cred;
66}
67
68static inline struct landlock_ruleset *landlock_get_current_domain(void)
69{
70 return landlock_cred(current_cred())->domain;
71}
72
73/*
74 * The call needs to come from an RCU read-side critical section.
75 */
76static inline const struct landlock_ruleset *
77landlock_get_task_domain(const struct task_struct *const task)
78{
79 return landlock_cred(__task_cred(task))->domain;
80}
81
82static inline bool landlocked(const struct task_struct *const task)
83{
84 bool has_dom;
85
86 if (task == current)
87 return !!landlock_get_current_domain();
88
89 rcu_read_lock();
90 has_dom = !!landlock_get_task_domain(task);
91 rcu_read_unlock();
92 return has_dom;
93}
94
95/**
96 * landlock_get_applicable_subject - Return the subject's Landlock credential
97 * if its enforced domain applies to (i.e.
98 * handles) at least one of the access rights
99 * specified in @masks
100 *
101 * @cred: credential
102 * @masks: access masks
103 * @handle_layer: returned youngest layer handling a subset of @masks. Not set
104 * if the function returns NULL.
105 *
106 * Returns: landlock_cred(@cred) if any access rights specified in @masks is
107 * handled, or NULL otherwise.
108 */
109static inline const struct landlock_cred_security *
110landlock_get_applicable_subject(const struct cred *const cred,
111 const struct access_masks masks,
112 size_t *const handle_layer)
113{
114 const union access_masks_all masks_all = {
115 .masks = masks,
116 };
117 const struct landlock_ruleset *domain;
118 ssize_t layer_level;
119
120 if (!cred)
121 return NULL;
122
123 domain = landlock_cred(cred)->domain;
124 if (!domain)
125 return NULL;
126
127 for (layer_level = domain->num_layers - 1; layer_level >= 0;
128 layer_level--) {
129 union access_masks_all layer = {
130 .masks = domain->access_masks[layer_level],
131 };
132
133 if (layer.all & masks_all.all) {
134 if (handle_layer)
135 *handle_layer = layer_level;
136
137 return landlock_cred(cred);
138 }
139 }
140
141 return NULL;
142}
143
144__init void landlock_add_cred_hooks(void);
145
146#endif /* _SECURITY_LANDLOCK_CRED_H */